Field of the Invention
The present invention relates to a device for estimating the roll angle of a vehicle body such as a motorcycle.
Description of Related Art
There are many cases where the roll angle (angle of tilt in the roll direction) of a vehicle body such as a motorcycle needs to be estimated successively in real time. For example, there is a case where estimated values of the roll angle of a vehicle body are required for traction control of a driving wheel of a motorcycle.
Japanese Patent Application Publication No. 2010-149681 proposes a technique of estimating the roll angle (“bank angle” in the description of Japanese Patent Application Publication No. 2010-149681) of a vehicle body to control the illumination range of a headlamp of a motorcycle, for example.
In this technique, an estimated value of the roll angle is calculated by: correcting a detection value of the roll rate by use of a correction amount, which is calculated so as to be approximated to a value of the roll angle in a state where a moment in the roll direction due to centrifugal force and a moment in the roll direction due to gravity obtained from detection values of yaw rate and vehicle speed are balanced; and integrating the corrected value.
In the technique proposed in Japanese Patent Application Publication No. 2010-149681, an estimated value of the roll angle is calculated by setting, as a convergence target value, a value of the roll angle in a state where a moment in the roll direction due to centrifugal force and a moment in the roll direction due to gravity are balanced.
Hence, there is a problem that an error in the estimated value of the roll angle tends to become large during slalom riding or in the transition period of a turning motion, when the roll angle of the vehicle body is not kept constant or substantially constant.